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Unread 09-27-2001, 11:27 AM   #1
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Join Date: May 2001
Location: NY
Posts: 533
which exhaust?

I'm changing the the 4.2 head to the 4.0 head in a '89 yj. Which exhaust will work with this application? is the Borla header worth the extra bucks? and which model would I order ?. I will need the o2 sensor port.

89 yj w/ mopar mpi and 4.0 head.94 ax-15 tranny and t-case, more mods comin.
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Unread 09-27-2001, 01:25 PM   #2
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1994 YJ Wrangler 
Join Date: Jul 2001
Location: Oceanside, CA, USA
Posts: 150
I've not been exceptionally impressed with the build quality of Borla headers I've seen in the past. The header tubes seem a bit thin, and I'm leery of their welds. However, it's been a while, so maybe they've improved since I last experienced one...?

Personally, I have a Thorley header and I love it. The part number is 634Y for F.I. heads. If your 4.0 head is off a fuelie Jeep, it should bolt right on.

Both the Thorley and the Borla have CARB EO numbers, and thus both have the O2 bung.
[b]'94 YJ Sahara Hardtop[/b]
4.0L / AX-15 / Stock NP231 / Stock D30 (open) / D60 (35-spline, Detroit locker, Moser axles) / rear disc brakes / 4.56 gears / Advanced Adapters SYE & CV Shaft / 33" BFG MT-KM's / Thorley Header / Magnaflow Muffler / BesTop Flares
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Unread 09-27-2001, 05:10 PM   #3
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Posts: 9
borlas work fine, but i believe custom made exhaust systems (by a specialist-important) can optimize the performance in the best way
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